Field of the Invention
The present invention relates to a magnetic sensor circuit, and more specifically to a configuration for preventing an erroneous detection and release at the occurrence of a fluctuation in a power supply voltage in a signal processing circuit that performs an offset cancel.
Background Art
A resistance bridge type magnetic sensor typified by a Hall effect switch uses a magnetoelectric transducer having a small magnetoelectric conversion coefficient and a relatively large offset voltage. In order to achieve high magnetic sensitivity precision, a signal processing circuit needs an offset cancel operation based on a clock signal. Further, there is a possibility that since an output signal from a sensor is small, a reference voltage for detecting a prescribed detection magnetic flux density or release magnetic flux density also becomes as small as a few tens of mV, and an erroneous detection or release will be done due to a fluctuation in the output of an amplifier and erroneous determination of a comparator, depending on timing with a reference clock signal having a width of a few V and used in signal processing when a power supply voltage fluctuates.
A related art magnetic sensor circuit has, for example, a voltage regulator incorporated therein and suppresses a fluctuation in a drive voltage in each of a sensor element and a signal processing circuit. Further, for example, the logic of a sensor output is latched plural times in a time-division manner, followed by a coincidence decision or a majority decision to decide an eventual output logic (refer to, for example, Patent Document 1).